Power generator and turbine unit

ABSTRACT

A power generator includes at least one underwater turbine unit providing a housing having a flow channel therethrough and at least one turbine means mounted in the flow channel for rotation in response to water flow through the flow channel. The turbine unit provides a turbine unit part releasably mountable in the turbine unit. The turbine unit part includes at least one of the at least one turbine means and a pump means. The turbine unit part is releasably mountable through an aperture in a side wall of the housing.

FIELD OF INVENTION

The present invention relates to a power generator and to a turbineunit. In particular, but not exclusively, the present invention relatesto an electrical power generator comprising an underwater turbine unitand to an underwater turbine unit.

BACKGROUND TO INVENTION

To meet increasing energy needs, there is a general desire to developenvironmentally friendly methods of generating electrical power. Oneparticular area of interest involves the generation of power using tidalenergy. This may be achieved by using underwater turbines.

Problems associated with known underwater turbines include the need tocarefully seal generator assemblies provided as part of the turbine toprevent the ingress of water, and also maintenance difficulties. This isbecause the complete turbine must be recovered to allow maintenance toany turbine part. There have also been difficulties in optimisingelectrical power generation.

It is amongst objects of one or more embodiments of at least one aspectof the present invention to obviate or mitigate at least one of theforegoing disadvantages.

It is a further object of one or more embodiments of the presentinvention to provide an underwater turbine unit driven by tidal orcurrent flow, and which can operate in ebb or flow tides without a needfor movement or rotation into the tidal direction.

SUMMARY OF INVENTION

According to a first aspect of the present invention, there is provideda power generator comprising:

at least one underwater turbine unit including a housing having a liquidflow channel therethrough and at least one turbine means mounted in theflow channel for rotation in response to liquid flow through the flowchannel.

Preferably the power generator comprises an electrical power generator.

Preferably, the flow channel defines a flow restriction.

Advantageously, this arrangement increases the velocity of liquidflowing through the flow channel in a restricted part of the flowchannel, relative to an unrestricted part of the flow channel. The flowrestriction preferably comprises a venturi, which may form part or theentire flow channel. In particular, the venturi may comprise adivergent-convergent-divergent venturi, tapering from openings at eitherend of the flow channel towards an inner part of the flow channel.

Preferably the housing is substantially symmetrical about a location ofthe at least one turbine means.

The venturi may comprise at least one first frusto-conical,frusto-pyramid or horn shaped body, optionally a cylindrical body, andan at least one second frusto-conical, frusto-pyramid or horn shapedbody.

In one embodiment a gap is provided between a divergent end of onefirst/second frusto-conical, frusto-pyramid or horn shaped body and anadjacent convergent end of one further first/second frusto-conical,frusto-pyramid or horn shaped body, the divergent end of the onefirst/second frusto-conical, frusto-pyramid or horn shaped body beingsmaller in diameter than the convergent end of the one furtherfirst/second frusto-conical, frusto-pyramid or horn shaped body.

Preferably the divergent end of the one first/second frusto-conical,frusto-pyramid or horn shaped body is substantially longitudinallycoincident with the convergent end of the one further first/secondfrusto-conical, frusto-pyramid or horn shaped body.

Preferably also, the power generator further comprises:

a pump means operatively coupled to the at least one turbine means;

a generator means driven by the turbine means and located separatelyfrom the at least one turbine unit; and

a fluid supply means coupling the pump means to the generator means forsupplying fluid from the pump means to the generator assembly forgenerating power.

Preferably the at least one/each underwater turbine unit is adapted tobe located in a body of water, eg on a floor or bed of a sea, ocean orriver. Preferably also the generator means is adapted to be locatedoutwith the body of water.

Preferably the liquid is provided from a body of water within which theturbine unit is submerged, and may be sea water. The fluid may comprisethe liquid.

The turbine housing may comprise an outer housing sleeve and an innerhousing sleeve, which inner sleeve may define the flow channel.Advantageously, this allows streamlining of the outer housing sleeve toreduce effects of tidal forces on the turbine unit as a whole.Alternatively, the turbine housing may comprise a single housing sleevewhich may define the flow channel.

The turbine means may comprise a single stage rotor and statorcombination, such as that disclosed in the Applicant's granted UK PatentNo. 2 302 348, the content of which is incorporated herein by reference,or a rotor only.

Alternatively, the turbine means may comprise a multiple stage rotor andstator combination, or any other suitable turbine means. In a furtheralternative, the turbine means may comprise a number of turbine bodiescoupled together, each including one or multiple stage rotor and statorcombinations.

The pump means may be coupled to the at least one turbine means, forexample, by an output shaft of the at least one turbine means. The pumpmeans may comprise a pump as disclosed in the Applicant's co-pending PCTPatent Publication No. WO 02/36964 the content of which is incorporatedherein by reference. The pump means may be mounted in the housing,preferably in the flow channel, and may be coupled directly to theturbine means. Alternatively, the pump means may be located separatelyfrom the turbine housing.

Preferably, the generator means is provided at surface, for example, atsea surface or on land. This is particularly advantageous in that itallows easy access to and maintenance of the generator means.Alternatively, the generator means may be provided underwater.

Preferably also, the generator means comprises a single generatorturbine means fed by the/each of the turbine units. The generator meansmay comprise a generator turbine means and a generator unit. Thegenerator turbine means may drive a generator unit directly, or througha gear mechanism, belt drive or other transmission system, to increasethe speed of rotation of the generator unit relative to the generatorturbine means. The generator unit may produce electrical power as eitheralternating current (AC) or direct current (DC), and may be controlledelectronically, which may allow control of output characteristics. Thegenerator turbine means may comprise a pelton wheel or other suitableturbine means, operatively coupled to the generator. Preferably, thegenerator turbine means is driven by the same liquid as the turbinemeans of the underwater turbine unit. Advantageously, therefore, theprovision of the pump means to supply liquid, in particular water suchas seawater, to the generator assembly allows a single liquid to be usedboth for driving the turbine unit turbine means and the generatorturbine means. Thus the generator unit of the generator means need onlybe sealed from the generator turbine means, and not from the surroundingenvironment.

Power generated by the generator means may be stored by or separatelyfrom the generator means, for example, by one or more batteries, or maybe fed directly into a power system, for example, a local power system.In the latter case, synchronisation, power factor and voltage of thepower generated may be regulated electronically prior to being fed intoa local power distribution mains system, eg grid. The generator meansmay be coupled by a cable, for example, a submarine cable, to the localpower distribution system.

The fluid supply means may comprise a conduit extending between the pumpmeans and the generator means. The fluid supply means is preferablyreleasably coupled to at least the pump means and/or the turbine means,to allow separation and removal of one or both of the pump means andturbine means for recovery to surface.

The turbine housing is preferably secured to an underwater surface, forexample, a floor or bed of a sea, ocean or river by, for example, amounting structure, which may be substantially aligned with thedirection of tidal flow. Alternatively, the turbine housing may bemoveably secured to an underwater surface to allow movement to face thedirection of main or tidal flow. The turbine unit may comprise a subseaturbine unit, but it will be appreciated that the turbine unit may beused in any underwater environment where a liquid flow exists, forexample, in any tidal or river flow situation.

Preferably the turbine unit also provides a turbine part releasablymountable in the turbine unit, the part including at least one of theturbine means to the pump means.

According to a second aspect of the present invention, there is provideda turbine unit for use in or when used in the power generator of thefirst aspect of the present invention.

According to a third aspect of the present invention, there is provideda power generator comprising:

at least one underwater turbine unit including at least one turbinemeans for rotation in response to liquid flow and a pump meansoperatively coupled to the at least one turbine means;

a generator means located separately from the at least one turbine unit;and

a fluid supply means coupling the pump means to the generator means forsupplying fluid from the pump means to the generator means forgenerating power.

Preferably the at least one/each underwater turbine unit is adapted tobe located in a body of water, eg on a floor or bed of sea, ocean orriver. Preferably also the generator means is adapted to be locatedoutwith the body of water.

Preferably the power generator generates electrical power.

Further preferably, the at least one turbine unit includes a housinghaving a flow channel therethrough, the at least one turbine means beingmounted in the flow channel for rotation in response to liquid flowthrough the flow channel. The generator means may be located separatelyfrom the turbine housing.

Preferably the liquid is provided from a body of water within which theturbine unit is submerged, and may be eg sea water. The fluid maycomprise the liquid.

Preferably the power generator comprises two or more underwater turbineunits, each turbine unit including a turbine means for rotation inresponse to fluid flow and a pump means operatively coupled to therespective turbine means;

the generator means being located separately from the turbine units; and

fluid supply means coupling each turbine unit pump means to thegenerator means for supplying fluid from each pump means to thegenerator means for generating power.

Preferably further, the generator means comprises a single generatormeans fed by each of the two or more turbine unit pump means.Advantageously, this allows a single generator means to be providedconnected to the two or more turbine units, such that a common singlegenerator means is provided, eg. to reduce construction and maintenancecosts.

The power generator may comprise a plurality, for example, three or moreturbine units, each turbine unit pump means being coupled to thegenerator means. Each turbine unit pump means may be coupled to thegenerator means by respective fluid supply means. In this fashion, fluidmay be supplied separately from the pump means of each turbine unit tothe remotely located generator means, where the fluid supplied by eachpump may be combined into a single stream for driving, for example agenerator turbine means of the generator means. Alternatively, the fluidsupply means may comprise means for combining the fluid from eachturbine unit pump means separately from or outside the generator means,for example, by a manifold, which may be an underwater manifold.

According to a fourth aspect of the present invention there is providedan underwater turbine unit including at least one turbine means forrotation in response to liquid flow and a pump means operatively coupledto the turbine unit means, the turbine unit also providing a turbineunit part realeasably mountable in the turbine unit, the part includingat least one of the at least one turbine means and the pump means.

The turbine unit may include a housing having a liquid flow channeltherethrough, the at least one turbine means mounted in the flow channelfor rotation in response to liquid fluid flow through the flow channel.The turbine part may comprise a turbine housing part releasablymountable in the turbine housing.

Preferably, also the turbine part comprises both the at least oneturbine means and the pump means.

Advantageously, this arrangement allows the turbine part, carrying theturbine means and the pump, to be released from the underwater turbineunit and removed or replaced, for example, for maintenance purposes. Inparticular, the turbine part may be recoverable to surface by releasingthe part from the turbine unit.

The turbine housing may include an opening or aperture to allow accessto the turbine housing part, which opening may be selectively closeable.The turbine housing may include an openable flap, door, catch, window orthe like selectively closing the opening to allow access to the turbinehousing part for removal. The turbine housing part may comprise a ringmember which may form part of the flow channel and which may house atleast part of one or both of the at least one turbine means and the pumpmeans.

According to a fifth aspect of the present invention, there is provideda power generator comprising:

an underwater turbine unit according to a fourth aspect of the presentinvention;

a generator means located separately from the turbine housing; and

a fluid supply means coupling the pump means to the generator means, forsupplying fluid from the pump means to the generator means forgenerating power.

The generator means may be located separately from the turbine housing.

According to a sixth aspect of the present invention there is provided aturbine housing part for an underwater turbine unit according to thefourth aspect of the present invention.

Further features of any one or more of the power generators defined inthe first, third or fifth aspects of the present invention may be sharedwith features of the power generators defined in any other one of thefirst, third or fifth aspects.

According to a seventh aspect of the present invention there is provideda method of generating electrical power using the power generator of anyof the first, third or fifth aspects of the present invention.

BRIEF DESCRIPTION OF DRAWINGS

Embodiments of the present invention will now be described, by way ofexample only, with reference to the accompanying drawings, which are:

FIG. 1 a schematic, perspective illustration of a power generator inaccordance with an embodiment of the present invention;

FIG. 2 an enlarged, partially sectioned view of an underwater turbineunit forming part of the power generator of FIG. 1;

FIG. 3 a schematic, perspective illustration of a power generator duringinstallation or maintenance in accordance with an alternative embodimentof the present invention;

FIG. 4 a side cross-sectional view of a housing of a turbine unitforming part of a power generator in accordance with a furtheralternative embodiment of the present invention;

FIG. 5 a perspective illustration of a housing of a turbine unit formingpart of a power generator in accordance with a still further alternativeembodiment of the present invention; and

FIG. 6 a side view of a turbine unit including the housing of FIG. 5.

DETAILED DESCRIPTION OF DRAWINGS

Referring firstly to FIG. 1, there is shown a power generator inaccordance with a first embodiment of the present invention, the powergenerator indicated generally by reference numeral 8. The powergenerator 8 generally comprises an underwater turbine unit 10, which isshown in the enlarged, partially sectioned view of FIG. 2. The turbineunit 10 includes a housing or shroud 12 having a fluid flow channel 14therethrough, a turbine means 16 mounted in the flow channel 14, forrotation in response to liquid flow through the fluid channel 14, and apump 18 operatively coupled to the turbine means 16. The power generator8 also includes a generator assembly 20 (FIG. 1) located separately fromthe turbine housing 12, and a fluid supply means 22 coupling the pump 18to the generator assembly 20, for supplying fluid from the pump 18 tothe generator assembly 20, for generating power.

FIG. 1 illustrates an embodiment of the present invention including twoor more, in particular four underwater turbine units 10, 10 a, 10 b and10 c. Each of the units 10 a-10 c are similar to the turbine unit 10 andlike components share the same reference numerals. The fluid supplymeans 22 couples each turbine unit pump 18 to the generator assembly 20.Each of the turbine units 10-10 c are mounted by respective mountingframes 11, 11 a, 11 b and 11 c to the seabed 13 and are aligned with themain direction of tidal flow, as indicated by the arrow B-B′.

In more detail, the turbine unit housing 12 includes an outer housingsleeve 24 and an inner housing sleeve 26, which defines the fluid flowchannel 14. The inner housing sleeve 26 is formed in the shape of adivergent-convergent-divergent venturi, which forms a flow restrictionin the fluid flow channel 14. This has the effect of increasing thevelocity of fluid flow through the flow channel 14 in the direction ofthe arrow A or A′. As can be seen from FIG. 1 or 2, the housing 12 issubstantially symmetrical in a longitudinal direction so that theturbine unit 10 is operative in either of two substantially opposingdirections.

The turbine means 16 comprises a single stage rotor 17 and stator 19combination, similar to that disclosed in the Applicant's granted UKPatent No. 2 302 348. The rotor 17 carries a number of rotor blades 21and the stator 19 a number of stator blades 23. The stator 19 is shownpartially cut-away in FIG. 2, for illustration purposes. The pump 18comprises a pump of the type disclosed in the Applicant's co-pending PCTPatent Publication No. WO 02/36964, and is coupled directly to theturbine means 16 by a turbine output shaft 28, for rotation with and bythe turbine means 16.

The fluid supply means comprises a fluid conduit 30, which couples thepump 18 to the generator assembly 20. In this fashion, liquid flowingthrough the liquid flow channel 14 drives the turbine means, to rotatethe rotor and thus the output shaft 28, driving the pump 18 to pumpfluid to the generator assembly 20. It will therefore be noted that thedriving liquid, in this case seawater, which drives the turbine means 16is also supplied by the pump 18 to the generator assembly 20.

The generator assembly 20 is mounted on a platform 32 mounted on theseabed 13, and generally comprises a generator turbine means (not shown)such as a pelton wheel and a generator unit (not shown) coupled to thepelton wheel. The pelton wheel is thus driven by fluid supplied from thepump 18 to rotate and drive the generator unit, to generate electricalpower.

In the power generator 8 shown in FIG. 1, each of the turbine units10-10 c are connected via respective conduits 30 to the generatorassembly 20, such that fluid is supplied to a common generator. Mountingof the generator assembly 20 separately from the housing, in particularat the surface on the platform 32, is particularly advantageous as thisboth assists in maintenance of the generator assembly 20 and reducesconstruction and maintenance costs. This is in part because thegenerator assembly is provided above the sea surface, and therefore doesnot to be sealed against the ingress of seawater.

The generator assembly 20 is connected via submarine cable to a localonshore power grid, to feed the AC or DC electrical power generateddirectly into the local grid. Alternatively, the generator assembly 20may include batteries (not shown) for storing the generated electricity.

It has been found that the turbine units 10, 10 a, 10 b, 10 c typicallyhave a liquid entry angle of ±25° from the longitudinal axis thereof,and therefore do not need to be aligned with ebb or flow tides.

Turning now to FIG. 3, a further feature of the power generator 8 ofFIG. 1 is illustrated, in accordance with an alternative embodiment ofthe present invention.

Each turbine unit 10-10 c includes a housing part 34 which is releasablymounted in the turbine housing 12. The housing part 34 carries theturbine means 16 and the pump 18, and is removable for maintenance, asillustrated in FIG. 3. To assist this operation, the outer housing part24 of the turbine housing 12 includes an opening 36 extending partlyaround the outer housing sleeve 24. A hatch 38 (FIG. 3) is opened toallow access to the housing part 34. Also, the conduit 30 includes aconnection 31, which couples the conduit 30 to a section 33 of conduitcoupled to the pump 18. In this fashion, the housing part 34 may beremoved for maintenance to the turbine means 16 and/or pump 18,following opening of the hatch 38 and release of the connection 31. FIG.3 shows a vessel 40 on site removing the housing part 34 formaintenance, using a crane 42. This is particularly advantageous as thisallows maintenance without having to remove the whole turbine unit 10from the seabed 13.

Preliminary calculations for the power generator 8 are based on thefollowing assumptions:

Power to be generated, P = 50 kW Velocity of tidal current, V₁ = 3 knots= 1.54 m/s Inlet to throat venturi ratio, A₁:A₂ = 4:1 Density of seawater, ρ = 1025 kg/m³ Hydraulic efficiency of 75% turbine meanspropellor/rotor = Efficiency of pump = 90% Efficiency of turbine means =85% Efficiency of generator unit = 90%

From the above, the overall efficiency of the system is 51.646, giving arequired power at propellers P_(p) of the turbine units, of

$P_{p} = {\frac{50\mspace{14mu}{kW}}{0.5164} = {96.8\mspace{14mu}{kW}}}$

From the theory of continuity, for an inlet to throat ratio of 4:1 andan inlet velocity of 1.54 m/s the velocity through the propeller at thethroat of the venturi, v₂ will beV ₂=4*1.54=6.16 m/s

The amount of power, P₀, available in a freely flowing fluid stream ofcross-sectional area, A, is equal to this area multiplied by thevelocity of the fluid stream and the kinetic energy of a unit volume ofthe fluid stream, and is given as:P ₀=(½·ρ·A·v ₁ ³)

Thus, the required venturi inlet area, A₁ is,

$A_{1} = {\frac{2*96830}{1025*1.54^{3}} = {51.7\mspace{14mu} m^{2}}}$

and the required venturi throat area, A₂ is 12.9 m². This is equivalentto a venturi inlet diameter of 8.09 m and throat diameter of 4.05 m.

At these parameters the turbine means 16 would be expected to rotate atapproximately 60 rpm in a 3 knot current.

From the equation for the calculation of P₀ above, it is evident thatthe velocity of the tidal stream has a significant effect on theavailable power. Using the above dimensions and assumptions, the effectof small increases in tidal velocity on the power that may be extractedis given below:

Velocity (knots Extracted power (kW) 3 50 4 118 5 230 6 397 7 631 8 942

(Effect of tidal velocity on power that may be extracted from a 4 mpropeller and housing inlet diameter of 8 m.)

Similarly, to generate 1 MW from a current with a mean velocity of 5knots would require turbine means blade/rotor of 8.5 diameter and aturbine housing 12 inlet of 17 m diameter.

Referring now to FIG. 4, there is shown a housing 12 of a turbine unit10 forming part of a power generator 8 in accordance with a furtheralternative embodiment of the present invention.

It has been found that if the liquid entry angle β to the turbine unit10 is to steep then liquid flow will separate at boundary layer D. Toenergise the boundary layer D and ensure liquid flow through the turbineunit 10, the venturi is adapted as described below.

As can be seen from FIG. 4, the venturi comprises at least onefrusto-conical body 100 a, 100 b, 100 c a cylindrical body 102 and an atleast second frusto-conical body 104 a, 104 b, 104 c.

In this embodiment a gap 106 is provided between a divergent end 108 ofone first/second frusto-conical body 100, 104 and an adjacent convergentend 110 of one further first/second frusto-conical body 100,104, thedivergent end 108 of the one first/second frusto-conical body 100,104being smaller in diameter than the convergent end 110 of the one furtherfirst/second frusto-conical body 100,104. The frusto-conical body may bestraight edged or concaved inwards.

As can be seen from FIG. 4, the divergent end 108 of the onefirst/second frusto-conical body 100,104 is substantially longitudinallycoincident with the convergent end 110 of the one further first/secondfrusto-conical body 100,104.

Typically the housing 12 has an overall length of around 20 m, the ends112 of the symmetrical venturi an internal diameter of 15 to 20 m andtypically around 17.5 m, the cylindrical body 102 a length of 2 m and aninternal diameter of 10 m. Typically the radial size of the gap 108 is 1m, and the further first/second frusto-conical body 100,104 has a lengthof 2 m.

Referring to FIGS. 5 and 6, there is shown a housing 12 of a turbineunit 10 forming part of a power generator 8 in accordance with a stillfurther alternative embodiment of the present invention.

In this embodiment, the venturi comprises a pair of frusto-conicalbodies 100 b and a pair of horn shaped bodies 100 a, gaps 106 beingprovided between each frusto-conical body 100 b, and adjacent hornshaped body 100 a.

It will be appreciated that various modifications may be made to theforegoing embodiments within the scope of the present invention. Forexample, the fluid supply means may comprise means for combining thefluid from each turbine unit pump separately from or outside thegenerator assembly, for example, by a manifold, which may be anunderwater manifold. The turbine housing may comprise a single housingsleeve which may define the flow channel. The turbine means may comprisea multiple stage rotor and stator combination, or any other suitableturbine means. The turbine means may comprise a number of turbine bodiescouples together, each including one or multiple stage rotor and statorcombinations. The pump may be located separately from the turbinehousing. The turbine housing may be moveably secured to an underwatersurface to allow movement to face the direction of main or tidal flow.The turbine means may include a rotor only, without a stator. Further,although in the disclosed embodiments the flow channel is advantageouslyof circular cross-section, other cross-sections are possible, eg oval,elliptical, square or rectangular.

1. A power generator comprising at least one underwater turbine unit,the at least one underwater turbine unit providing: a housing having aliquid flow channel therethrough, at least one turbine means mounted inthe flow channel for rotation in response to liquid flow through theflow channel, and a pump means mounted in the flow channel, the pumpmeans being operatively coupled to the at least one turbine means, suchthat, in use, liquid flow through the flow channel causes rotation ofthe at least one turbine means, which drives the pump means which pumpsa fluid, and wherein the fluid comprises the liquid, wherein the powergenerator further comprises a generator means driven by the turbinemeans and located separately from the at least one underwater turbineunit, and a fluid supply means coupling the pump means to the generatormeans for supplying fluid from the pump means to the generator assemblyfor generating power, wherein the fluid supply means comprises a conduitextending between the pump means and the generator means, and the fluidsupply means is releasably coupled to at least one of the pump means andthe turbine means to allow separation and removal of at least one of thepump means and the turbine means for recovery to a surface of a body ofwater.
 2. A power generator as claimed in claim 1, wherein an apertureextends through a side wall of the housing.
 3. A power generator asclaimed in claim 1, wherein the at least one underwater turbine unit isadapted to be located at least one of on and adjacent to a bottom of abody of water.
 4. A power generator as claimed in claim 1, wherein thepower generator comprises an electrical power generator.
 5. A powergenerator as claimed in claim 1, wherein the flow channel defines a flowrestriction.
 6. A power generator as claimed in claim 5, wherein theflow restriction comprises a venturi.
 7. A power generator as claimed inclaim 6, wherein the venturi comprises a divergent-convergent-divergentventuri, which tapers from openings at either end of the flow channeltoward an inner part of the flow channel.
 8. A power generator asclaimed in claim 6, wherein the venturi comprises one first body, acylindrical body, and at least one second body, and the first and secondbodies are each at least one of a frusto-conical body, afrusto-pyramidal body, and a horn-shaped body.
 9. A power generator asclaimed in claim 8, wherein a gap is provided between a divergent end ofa chosen first or second body and an adjacent convergent end of anotherfirst or second body, the divergent end of the chosen first or secondbody being smaller in diameter than the convergent end of the anotherfirst or second body.
 10. A power generator as claimed in claim 8,wherein a divergent end of a chosen first or second body issubstantially longitudinally coincident with a convergent end of anotherfirst or second body.
 11. A power generator as claimed in claim 1,wherein the housing is substantially longitudinally and transverselysymmetrical about a mid-point location of the at least one turbinemeans.
 12. A power generator as claimed in claim 1, wherein the at leastone underwater turbine unit is adapted to be located in a body of waterand the generator means is adapted to be located outside the body ofwater.
 13. A power generator as claimed in claim 1, wherein the housingcomprises an outer housing sleeve and an inner housing sleeve, and theinner housing sleeve defines the flow channel.
 14. A power generator asclaimed in claim 1, wherein the turbine means is at least one of asingle stage rotor and stator combination; a rotor only; a multiplestage rotor and stator combination; and a number of turbine bodiescoupled together, each including at least one of a single stage and amultiple stage rotor and stator combination.
 15. A power generator asclaimed in claim 1, wherein the pump means is coupled to the at leastone turbine means by an output shaft of the at least one turbine means.16. A power generator as claimed in claim 1, wherein the pump means iscoupled directly to the turbine means.
 17. A power generator as claimedin claim 1, wherein the generator means is provided at a surface of abody of water.
 18. A power generator as claimed in claim 1, wherein thegenerator means comprises a generator unit and a single generatorturbine means fed by the at least one underwater turbine unit, thegenerator turbine means driving the generator unit.
 19. A powergenerator as claimed in claim 18, wherein the generator unit produceselectrical power as at least one of alternating current (AC) and directcurrent (DC).
 20. A power generator as claimed in claim 18, wherein thegenerator turbine means comprises a pelton wheel operatively coupled tothe generator, and the generator turbine means is driven by the sameliquid as drives the turbine means of the underwater turbine unit.
 21. Apower generator as claimed in claim 1, wherein power generated by thegenerator means is at least one of stored by the generator means, storedseparately from the generator means, and fed directly into a powersystem.
 22. A power generator as claimed in claim 1, wherein the housingis secured to an underwater surface by a mounting structure so as tosubstantially align the housing with a direction of tidal flow.
 23. Apower generator as claimed in claim 1, wherein the turbine unitcomprises a turbine part releasably mountable in the turbine unit, theturbine part including at least one of the turbine means and the pumpmeans.
 24. A power generator as claimed in claim 1, wherein the at leastone turbine means is adapted such that, in use, liquid flow through theflow channel in either direction through the housing causes rotation ofthe at least one turbine means, which drives the pump means which pumpsthe fluid.
 25. A power generator as claimed in claim 1, wherein thehousing comprises first and second ends, and the first and second endseach flare outwards from the housing.
 26. A power generator as claimedin claim 1, wherein the housing is substantially symmetrical about amid-point whereof, the housing comprises first and second ends, whichfirst and second ends each flare outwards from the housing, wherein theat least one turbine means is located at the mid-point of the housing,and the at least one turbine means is adapted such that, in use, waterflow through the flow channel in either direction causes rotation of theat least one turbine means, which drives the pump means which pumps thefluid.